The adaptation of the gastrointestinal tract after extensive small bowel resection will be studied in several ways. Gastric secretion and mucosal proliferation will be measured after both proximal and distal bowel resection. Levels of circulating gastrin will be determined to see if this is the mechanism of changes in the gastric mucosa. Organ cultures of small bowel mucosa will be stimulated with serum from resected animals to see if there is a circulating factor which stimulates small bowel mucosal growth. Various enzymes will be measured which may participate in the adaptive response by the small intestine. In other studies, the metabolism of circulating maltose will be further investigated in man and rats. Its possible role as a substrate for parenteral hyperalimentation should be evaluated in long term infusion studies.